New 'butterfly of the sea' species discovered

A case of mistaken identity that took more than 16 years to detect recently culminated in a new species of vibrant sea creature confirmed in WA's North West.

Nudibranchs are soft-bodied gastropod molluscs, which are commonly confused with sea slugs because they shed their shells early on in life.

An estimated 3000 species occur in oceans across the world, and their colours, body shapes and undulated swimming style has earned them the nickname "butterflies of the sea."

This week, a new species will be added to the list, after a competition by the WA Museum and ABC Radio National's Off Track program as part of National Science Week.

The competition offers the public the chance of a lifetime to contribute to the new species name, in what is believed to be an Australian first.

Previously mistaken as Moridilla brockii, the species was confirmed to be completely new to science after recent scrutiny by WA Museum Aquatic Zoology Senior Research Scientist Dr Nerida Wilson, with help from Spanish nudibranch expert Dr Leila Carmona.

Dr Wilson was first dazzled by the colourful creature while scuba diving the Dampier Archipelago, about 1550kms north of Perth, in 2000.

"I was really impressed by its amazing defence displays," she says.

When threatened, the nudibranch quickly unfurls sausage-like tentacles, called cerata, on its back, in an attempt to appear larger and scare off predators.

"It's quite an interesting way of telling others to get lost," Dr Wilson says.

Despite first attracting her attention 16 years ago, Dr Wilson only started analysing preserved specimens, photographs and DNA samples of M. brockii this year, as part of a new study of the biodiversity of WA's North West coast.

"Nudibranchs are my first love, so I paid particular attention to them," Dr Wilson says.

"It was only a few months ago that we realised it was definitely a different species."

Things that set this nudibranch apart from others include its size, anatomy, colouring and distribution.

An adult can measure up to 10cm, which is larger than the average sea slug size of 1-2cm, and they have been consistently recorded at Ningaloo, Exmouth, off the coast of the Kimberley and Pilbara, up to Darwin.

Dr Wilson says more than 2500 submissions were received.

"I've been so impressed with the entries," she says.

"It's really humbling to realise how many people have sat down and really thought about this and come up with some really cool names."

The name will be announced Saturday, August 20 on Off Track at 10.30am.

The scientists will then submit a scientific paper to a journal for peer review.

If it is accepted, it will become the official name for Moridilla sp.

This article first appeared on ScienceNetwork Western Australia a science news website based at Scitech.